Isolation and characterization of a lipopeptide bioemulsifier produced by Pseudomonas nitroreducens TSB.MJ10 isolated from a mangrove ecosystem

Simultaneous nitrate and phosphorus removal in novel steel slag biofilters: Optimization and mechanism study

The simultaneous nitrate (NO3--N) and phosphorus (P) removal systems are considered to be an effective wastewater treatment technology. However, so far, there are few studies on system optimization to improve NO3--N and P removal. In this study, nine simultaneous NO3--N and P removal biofilters (SNPBs) were constructed to treat simulated wastewater. In order to optimize the NO3--N and P removal, different material loading positions were set: (1) red soil, steel slag, and rice straw (RSR), (2) steel slag, red soil, and rice straw (SRR), and (3) red soil, rice straw, and steel slag (RRS). Results showed that the above three treatments had mean removal efficiencies of 58%-91% for NO3--N and 55%-81% for TP, with the best N and P removal occurring in the SRR. The TN mass balance indicated that microbial removal was responsible for 78.2% of the influent TN in the SRR biofilter. The key microorganisms were Enterobacter, Klebsiella, Pseudomonas, Diaphorobacter, and unclassified_f_Enterobacteriaceae, which accounted for 61.9% of the total microorganisms. The main P-removal mechanism was the formation of Al-P, Fe-P, and Ca-P in red soil or steel slag layer. In addition, the decrease of SRR effluent pH from 11.86 in 1-7 days to 7.75 in 8-50 days indicated that red soil and rice straw had a synergistic effect on water pH reduction. These results suggest that a reasonable combination of steel slag with red soil and rice straw not only simultaneously removes NO3--N and P but also additionally solves the problem of high pH caused by steel slag.

Production and structural characterization of eco-friendly bioemulsifier SC04 from Saccharomyces cerevisiae strain MYN04 with potential applications

BACKGROUND

Bioemulsifiers are natural or microbial-based products with the ability to emulsify hydrophobic compounds in water. These compounds are biodegradable, eco-friendly, and find applications in various industries.

RESULTS

Thirteen yeasts were isolated from different sources in Alexandria, Egypt, and evaluated for their potential to produce intracellular bioemulsifiers. One yeast, isolated from a local market in Egypt, showed the highest emulsification index (EI24) value. Through 26S rRNA sequencing, this yeast was identified as Saccharomyces cerevisiae strain MYN04. The growth kinetics of the isolate were studied, and after 36 h of incubation, the highest yield of cell dry weight (CDW) was obtained at 3.17 g/L, with an EI24 of 55.6%. Experimental designs were used to investigate the effects of culture parameters on maximizing bioemulsifier SC04 production and CDW. The study achieved a maximum EI24 of 79.0 ± 2.0%. Furthermore, the crude bioemulsifier was precipitated with 50% ethanol and purified using Sephadex G-75 gel filtration chromatography. Bioemulsifier SC04 was found to consist of 27.1% carbohydrates and 72.9% proteins. Structural determination of purified bioemulsifier SC04 was carried out using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX), high-performance liquid chromatography (HPLC), and nuclear magnetic resonance spectroscopy (NMR). FTIR spectroscopy revealed characteristic bands associated with carboxyl and hydroxyl groups of carbohydrates, as well as amine groups of proteins. HPLC analysis of monosaccharide composition detected the presence of mannose, galactose, and glucose. Physicochemical characterization of the fraction after gel filtration indicated that bioemulsifier SC04 is a high molecular weight protein-oligosaccharide complex. This bioemulsifier demonstrated stability at different pH values, temperatures, and salinities. At a concentration of 0.5 mg/mL, it exhibited 51.8% scavenging of DPPH radicals. Furthermore, in vitro cytotoxicity evaluation using the MTT assay revealed a noncytotoxic effect of SC04 against normal epithelial kidney cell lines.

CONCLUSIONS

This study presents a new eco-friendly bioemulsifier, named SC04, which exhibits significant emulsifying ability, antioxidant and anticancer properties, and stabilizing properties. These findings suggest that SC04 is a promising candidate for applications in the food, pharmaceutical, and industrial sectors.

Efficiency and kinetics of Assam crude oil degradation by Pseudomonas aeruginosa and Bacillus sp

We report kinetics of Assam crude oil degradation by Pseudomonas aeruginosa AKS1 and Bacillus sp. AKS2, both isolated from Assam refinery sediments. The isolates exhibited appreciable degrees of hydrophobicity, emulsification index and biosurfactant production. Crude oil degradation efficiency of isolates was assessed in (1) liquid medium amended with 1% v/v crude oil and (2) microcosm sediments (125 mg crude oil/ 10 g sand). In liquid culture, biodegradation rate (k) and half-life (t_1/2) values were found to be 0.038 day^-1 and 18.09 days for P. aeruginosa AKS1, and 0.020 day^-1 and 33.97 days in case of Bacillus sp. AKS2, respectively. In microcosm sediments, the estimated k and t _1/2 values were 0.014 day^-1 and 50 days for P. aeruginosa AKS1, and 0.011 day^-1 and 61.34 days in case of Bacillus sp. AKS2. The level of nutrient treatment in microcosm sand sediment was 125 µg N and 62.5 µg P/g sediment in case of P. aeruginosa AKS1 and 375 µg N and 37.5 µg P/g sediment in case of Bacillus sp. AKS2. In microcosms without inorganic nutrients, values of k and t_1/2 were found to be 0.007 day^-1 and 100 days for P. aeruginosa AKS1 and for Bacillus sp. AKS2, the respective values were 0.005 day^-1 and 150.68 days. Our data provides important information for predictive hydrocarbon degradation in liquid medium and contaminated sediments.

Isolation and characterization of a novel rhamnolipid producer Pseudomonas sp. LGMS7 from a highly contaminated site in Ain El Arbaa region of Ain Temouchent, Algeria

This study aims to isolate and characterize a novel rhamnolipid producer within the recent bioremediation approaches for treating hydrocarbon-contaminated soils in Algeria. In this context, from a hydrocarbon-contaminated soil, a newly bacterium designated LGMS7 was screened and identified, belonged to the Pseudomonas genus, and was closely related to Pseudomonas mucidolens, with a 16S rRNA sequence similarity of 99.05%. This strain was found to use different hydrocarbons and oils as a sole carbon and energy source for growth. It showed a stable emulsification index E₂₄ (%) of 66.66% ± 3.46 when growing in mineral salts medium (MSM) supplemented with 2% (v/v) glycerol after incubation for 6 days at 30 °C. Interestingly, it was also able to reduce the surface tension of the cell-free supernatant to around 30 ± 0.65 mN m^-1 with a critical micelle concentration (CMC) of 800 mg l^-1. It was found to be able to produce around 1260 ± 0.57 mg l^-1 as the yield of rhamnolipid production. Its biosurfactant has demonstrated excellent stability against pH (pH 2.0-12.0), salinity (0-150 g l^-1), and temperature (-20 to 121 °C). Based on various chromatographic and spectroscopic techniques (i.e., TLC, FTIR, ¹H-NMR), it was found to belong to the glycolipid class (i.e., rhamnolipids). Taken altogether, the strain LGMS7 and its biosurfactant display interesting biotechnological capabilities for the bioremediation of hydrocarbon-contaminated sites. To the best of our knowledge, this is the first study that described the production of biosurfactants by Pseudomonas mucidolens species.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-021-02751-6.

Biophysical approaches for exploring lipopeptide-lipid interactions

In recent years, lipopeptides (LPs) have attracted a lot of attention in the pharmaceutical industry due to their broad-spectrum of antimicrobial activity against a variety of pathogens and their unique mode of action. This class of compounds has enormous potential for application as an alternative to conventional antibiotics and for pest control. Understanding how LPs work from a structural and biophysical standpoint through investigating their interaction with cell membranes is crucial for the rational design of these biomolecules. Various analytical techniques have been developed for studying intramolecular interactions with high resolution. However, these tools have been barely exploited in lipopeptide-lipid interactions studies. These biophysical approaches would give precise insight on these interactions. Here, we reviewed these state-of-the-art analytical techniques. Knowledge at this level is indispensable for understanding LPs activity and particularly their potential specificity, which is relevant information for safe application. Additionally, the principle of each analytical technique is presented and the information acquired is discussed. The key challenges, such as the selection of the membrane model are also been briefly reviewed.

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A brief overview of topics to understand the generalities of lipopeptide (LP) science.

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Main analytical techniques used to reveal the interaction and the distorting effect of LP on artificial membranes.

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Guidelines for selecting of the most adequate membrane models for the given analytical technique.

Production and properties of a bioemulsifier obtained from a lactic acid bacterium

In the present work, the production of bioemulsifier (BE) by a lactic acid bacterium (LAB) grown at 25 °C in lactic whey-based media for 24 h was evaluated. Maximum production was detected in a medium containing yeast extract, peptone and lactic whey (LAP_LW medium), with a yield of 270 mg L^-1. The BE proved to be more innocuous for Caco-2 cells, used as a toxicological indicator, than the non-ionic surfactant Triton X-100. In addition, the microbial product presented higher stability to changes in temperature (37 °C to 100 °C), pH (2-10), and salt concentration (5% and 20%, w/v) than the synthetic surfactant. Regarding emulsifying capacity tested against different hydrophobic substrates (kerosene, motor oil, diesel, sunflower oil, and grape oil), the BE displayed E₂₄ values similar to or even better than those of Triton X-100. Finally, Triton X-100 caused irreversible modifications on the giant unilamellar vesicles (used as model membrane system), promoting the solubilization of the lipid bilayers. Nevertheless, BE induced temporary modifications of the membrane, which is associated with incorporation of the bioproduct in the outer layer. These results demonstrate the role of BE in biological processes, including reversible changes in microbial membranes to enhance the access to hydrophobic substrates.

Oil-in-water emulsion breaking marine bacteria for demulsifying oily wastewater

Oily wastewater is a large waste stream produced by a number of industries. This wastewater often forms stable oil-in-water (O/W) emulsion. These emulsions require demulsification in order to effectively treat the water prior to release. Although biological demulsification of O/W emulsion has advantages over traditional approaches, its development is at a preliminary stage with few demulsifying bacteria reported and a need for effective screening methods for such bacteria. In this study, thirty-seven marine O/W emulsion demulsifying bacterial strains belonging to 5 genera and 15 species were reported. Cell hydrophobicity and interfacial activity played key roles in the emulsion breaking. One of the highly effective demulsifying bacteria, Halomonas venusta strain N3-2A was identified and characterized. Both its extracellular biosurfactant and cell surface contributed to demulsification resulting in breaking of 92.5% of the emulsion within 24 h. A high throughput and effective screening strategy targeting O/W emulsion breaking bacteria using oil spreading test coupled with cell hydrophobicity test was proposed. In addition, the 37 demulsifying bacteria showed a certain degree of species/genus specific patterns of surface activity and cell hydrophobicity. The reported bacteria and the screening strategy have promising potential for the biological demulsification of O/W emulsions and oily wastewater treatment.

Characterization of biosurfactant lipopeptide and its performance evaluation for oil-spill remediation

Biosurfactant lipopeptide is a promising dispersant over varieties of chemical ones in oil-spill remediation. The toxicity, biodegradability and performance of the biosurfactant lipopeptide are studied in this paper.

Biosurfactant lipopeptide is a promising dispersant over varieties of chemical ones in oil-spill remediation.

Characterization, phylogenetic distribution and evolutionary trajectories of diverse hydrocarbon degrading microorganisms isolated from refinery sludge

Phylogenic association between bacteria living under harsh conditions can provide important information on adaptive mechanism, survival strategy and their potential application. Indigenous microorganisms isolated from toxic refinery oily sludge with ability to degrade a diverse range of hydrocarbons were identified and characterized. The strains including Pseudomonas aeruginosa RS1, Microbacterium sp. RS2, Bacillus sp. RS3, Acinetobacter baumannii RS4 and Stenotrophomonas sp. RS5 could utilize n-alkanes, cycloalkanes, polynuclear aromatic hydrocarbons (PAHs) with 2-4 rings and also substituted PAHs as sole substrate. The phylogenetic position of Bacillus sp. RS3 and Pseudomonas sp. RS1 was tested by applying the maximum likelihood (ML) method to the aligned 16S rRNA nucleotide sequences of PAH and aliphatic hydrocarbon degrading strains belonging to the corresponding genus. The base substitution matrix created with each set of organisms capable of degrading aromatic and aliphatic hydrocarbons showed significant transitional event with high values of transition: transversion ratio (R) under all conditions. The guanine-cytosine (GC) content of the hydrocarbon degrading test strains was also found to be highest for the clade which harbored them. The test strains consistently occupied a distinct terminal end within the phylogenetic tree constructed by ML analysis. This study reveals that the refinery sludge imposed environmental stress on the bacterial strains which possibly caused significant genetic alteration and phenotypic adaptation. Due to the divergent evolution of the Pseudomonas and Bacillus strains in the sludge, they appeared distinctly different from other hydrocarbon degrading strains of the same genus.

Isolation of nitrate-reducing bacteria from an offshore reservoir and the associated biosurfactant production

Biosurfactant producing nitrate-reducing bacteria (NRB) in anaerobic reservoir environments are closely associated with souring (H₂S) control in the offshore oil and gas industry. Five NRB strains were screened from offshore produced water samples and all were identified as Pseudomonas stutzeri. Their biosurfactant producing abilities when fed on either glucose or glycerol media were investigated. P. stutzeri CX3 reduced the medium surface tension to 33.5 and 29.6 mN m⁻¹, respectively, while growing on glucose or glycerol media. The CX3 strain was further inoculated to examine its growth performance, resulting in 32.4% and 94.5% of nitrate consumption over 228 hours of monitoring in two media, respectively. The composition analysis of the biosurfactant product generated by P. stutzeri CX3 was conducted through thin-layer chromatography, gas chromatography with a flame ionization detector (FID) and Fourier transform infrared spectroscopy (FT-IR). The biosurfactant product was identified as a mixture of a small part of lipopeptides and a large part of glycolipids while its critical micellar concentration (CMC) was as low as 35 mg L⁻¹. The biosurfactant product demonstrated high stability over a wide range of temperature (4–121 °C), pH (2–10), and salinity (0–20% w/v) concentration. The results provided valuable technical and methodological support for effective offshore reservoir souring control and associated enhanced oil recovery activities.

Biosurfactant producing nitrate-reducing bacteria (NRB) in anaerobic reservoir environments are closely associated with souring (H₂S) control in the offshore oil and gas industry.

Marinobacter sp. from marine sediments produce highly stable surface-active agents for combatting marine oil spills

Background

The application of chemical dispersants as a response to marine oil spills is raising concerns related to their potential toxicity also towards microbes involved in oil biodegradation. Hence, oil spills occurring under marine environments necessitate the application of biodispersants that are highly active, stable and effective under marine environment context. Biosurfactants from marine bacteria could be good candidates for the development of biodispersant formulations effective in marine environment. This study aimed at establishing a collection of marine bacteria able to produce surface-active compounds and evaluating the activity and stability of the produced compounds under conditions mimicking those found under marine environment context.

Results

A total of 43 different isolates were obtained from harbor sediments. Twenty-six of them produced mainly bioemulsifiers when glucose was used as carbon source and 16 were biosurfactant/bioemulsifiers producers after growth in the presence of soybean oil. Sequencing of 16S rRNA gene classified most isolates into the genus Marinobacter. The produced emulsions were shown to be stable up to 30 months monitoring period, in the presence of 300 g/l NaCl, at 4 °C and after high temperature treatment (120 °C for 20 min). The partially purified compounds obtained after growth on soybean oil-based media exhibited low toxicity towards V. fischeri and high capability to disperse crude oil on synthetic marine water.

Conclusions

To the best of our knowledge, stability characterization of bioemulsifiers/biosurfactants from the non-pathogenic marine bacterium Marinobacter has not been previously reported. The produced compounds were shown to have potential for different applications including the environmental sector. Indeed, their high stability in the presence of high salt concentration and low temperature, conditions characterizing the marine environment, the capability to disperse crude oil and the low ecotoxicity makes them interesting for the development of biodispersants to be used in combatting marine oil spills.

Electronic supplementary material

The online version of this article (10.1186/s12934-017-0797-3) contains supplementary material, which is available to authorized users.

Biosurfactant-biopolymer driven microbial enhanced oil recovery (MEOR) and its optimization by an ANN-GA hybrid technique

A lipopeptide biosurfactant produced by marine Bacillus megaterium and a biopolymer produced by thermophilic Bacillus licheniformis were tested for their application potential in the enhanced oil recovery. The crude biosurfactant obtained after acid precipitation effectively reduced the surface tension of deionized water from 70.5 to 28.25mN/m and the interfacial tension between lube oil and water from 18.6 to 1.5mN/m at a concentration of 250mgL^-1. The biosurfactant exhibited a maximum emulsification activity (E₂₄) of 81.66% against lube oil. The lipopeptide micelles were stabilized by addition of Ca²⁺ ions to the biosurfactant solution. The oil recovery efficiency of Ca²⁺ conditioned lipopeptide solution from a sand-packed column was optimized by using artificial neural network (ANN) modelling coupled with genetic algorithm (GA) optimization. Three important parameters namely lipopeptide concentration, Ca²⁺ concentration and solution pH were considered for optimization studies. In order to further improve the recovery efficiency, a water soluble biopolymer produced by Bacillus licheniformis was used as a flooding agent after biosurfactant incubation. Upon ANN-GA optimization, 45% tertiary oil recovery was achieved, when biopolymer at a concentration of 3gL^-1 was used as a flooding agent. Oil recovery was only 29% at optimal conditions predicted by ANN-GA, when only water was used as flooding solution. The important characteristics of biopolymers such as its viscosity, pore plugging capabilities and bio-cementing ability have also been tested. Thus, as a result of biosurfactant incubation and biopolymer flooding under the optimal process conditions, a maximum oil recovery of 45% was achieved. Therefore, this study is novel, timely and interesting for it showed the combined influence of biosurfactant and biopolymer on solubilisation and mobilization of oil from the soil.

A novel bioemulsifier produced by Exiguobacterium sp. strain N4-1P isolated from petroleum hydrocarbon contaminated coastal sediment

In this study,ExiguobacteriumN4-1P is reported as a bioemulsifier producer for the first time.

Review lipopeptides biosurfactants: Mean classes and new insights for industrial, biomedical, and environmental applications

Lipopeptides are microbial surface active compounds produced by a wide variety of bacteria, fungi, and yeast. They are characterized by high structural diversity and have the ability to decrease the surface and interfacial tension at the surface and interface, respectively. Surfactin, iturin, and fengycin of Bacillus subtilis are among the most popular lipopeptides. Lipopepetides can be applied in diverse domains as food and cosmetic industries for their emulsification/de-emulsification capacity, dispersing, foaming, moisturizing, and dispersing properties. Also, they are qualified as viscosity reducers, hydrocarbon solubilizing and mobilizing agents, and metal sequestering candidates for application in environment and bioremediation. Moreover, their ability to form pores and destabilize biological membrane permits their use as antimicrobial, hemolytic, antiviral, antitumor, and insecticide agents. Furthermore, lipopeptides can act at the surface and can modulate enzymes activity permitting the enhancement of the activity of certain enzymes ameliorating microbial process or the inhibition of certain other enzymes permitting their use as antifungal agents. This article will present a detailed classification of lipopeptides biosurfactant along with their producing strain and biological activities and will discuss their functional properties and related applications.

Anoxic biodegradation of petroleum hydrocarbons in saline media using denitrifier biogranules

The total petroleum hydrocarbons (TPH) biodegradation was examined using biogranules at different initial TPH concentration and contact time under anoxic condition in saline media. The circular compact biogranules having the average diameter between 2 and 3mm were composed of a dense population of Bacillus spp. capable of biodegrading TPH under anoxic condition in saline media were formed in first step of the study. The biogranules could biodegrade over 99% of the TPH at initial concentration up to 2g/L at the contact time of 22h under anoxic condition in saline media. The maximum TPH biodegradation rate of 2.6 gTPH/gbiomass.d could be obtained at initial TPH concentration of 10g/L. Accordingly, the anoxic biogranulation is a possible and promising technique for high-rate biodegradation of petroleum hydrocarbons in saline media.

Screening concepts, characterization and structural analysis of microbial-derived bioactive lipopeptides: a review

Lipopeptide biosurfactants are surface active biomolecules that are produced by a variety of microorganisms. Microbial lipopeptides have gained the interest of microbiologists, chemists and biochemists for their high biodiversity as well as efficient action, low toxicity and good biodegradability in comparison to synthetic counterparts. In this report, we review methods for the production, isolation and screening, purification and structural characterization of microbial lipopeptides. Several techniques are currently available for each step, and we describe the most commonly utilized and recently developed techniques in this review. Investigations on lipopeptide biosurfactants in natural products require efficient isolation techniques for the characterization and evaluation of chemical and biological properties. A combination of chromatographic and spectroscopic techniques offer opportunities for a better characterization of lipopeptide structures, which in turn can lead to the application of lipopeptides in food, pharmaceutical, cosmetics, agricultural and bioremediation industries.

Structural Analysis of the Lipopeptide Produced by the Bacillus subtilis Mutant R2-104 with Mutagenesis

The lipopeptide and its homologues are a kind of the five major biosurfactants with prominent interfacial and biological activities. A suite of mutagenesis method was adopted to expose a wild lipopeptide-producing strain Bacillus subtilis HSO121 to improve lipopeptide yield, and a stable mutant named R2-104 with a 2.0-fold production of lipopeptide was obtained. Compared to that of the wild strain HSO121, the lipopeptide produced by R2-104 showed a similar surface activity, but the course profiles of lipopeptide production during cultivation were different, with the peak yield of 500 mg at about 9 h by R2-104, and 400 mg at about 5 h by HSO121. The constituent abundance of the lipopeptide homologues produced by R2-104 was also different from that by HSO121. Combined methods of ESI-MS, GC-MS and MS-MS were applied for structural characterization of lipopeptide homologues, and it showed that the lipopeptides produced by R2-104 and HSO121 were attributed to a surfactin family with different constituents. The dominant constituent of the surfactin family produced by R2-104 was anteiso C15-surfactin with a relative content of 43.8 %, while the dominant one produced by HSO121was iso C14-surfactin with a relative content of 33.1 %.

A novel bioemulsifier from Geobacillus stearothermophilus A-2 and its potential application in microbial enhanced oil recovery

A novel glycoprotein emulsifier from the thermophilic, facultative anaerobic strain A-2 showing excellent, stable emulsifying properties and its potential application in MEOR.

Production and characterization of surfactin-type lipopeptides as bioemulsifiers produced by a Pinctada martensii-derived Bacillus mojavensis B0621A

Bacillus mojavensis B0621A was isolated from the mantle of a pearl oyster Pinctada martensii collected from South China Sea. Semi-purified surfactins (225 mg L(-1)) were obtained by acid precipitation and vacuum flash chromatography. The component of the semi-purified surfactins was preliminarily analyzed by liquid chromatography mass spectrometer system, and the results showed that all these surfactins could be a group of homologues. Eight surfactin homologues were isolated and afforded by reversed phase high-performance liquid chromatography. Furthermore, their structure was characterized by mass spectrometry analysis combined with nuclear magnetic resonance spectroscopy techniques. These surfactins shared seven amino acids as peptide backbone and a saturated β-hydroxy fatty acid chain residue (from C13 to C15), differed each other from peptide sequence in the position of Leu7 or Val7. All these surfactins had significant activity and stability of emulsification under various pH (from 7.0 to 12.0), temperature range (from 20 to 115 °C) and sodium chloride concentration (from 2.5 to 20.0 %, w/v). Taken all together, these results indicated that B. mojavensis B0621A have potential to be an alternative source as a biological-derived emulsifying agent.

Screening of biosurfactant-producing bacteria from offshore oil and gas platforms in North Atlantic Canada

From offshore oil and gas platforms in North Atlantic Canada, crude oil, formation water, drilling mud, treated produced water and seawater samples were collected for screening potential biosurfactant producers. In total, 59 biosurfactant producers belong to 4 genera, namely, Bacillus, Rhodococcus, Halomonas, and Pseudomonas were identified and characterized. Phytogenetic trees based on 16S ribosomal deoxyribonucleic acid (16S rDNA) were constructed with isolated strains plus their closely related strains and isolated strains with biosurfactant producers in the literature, respectively. The distributions of the isolates were site and medium specific. The richness, diversity, and evenness of biosurfactant producer communities in oil and gas platform samples have been analyzed. Diverse isolates were found with featured properties such as effective reduction of surface tension, producing biosurfactants at high rate and stabilization of water-in-oil or oil-in-water emulsion. The producers and their corresponding biosurfactants had promising potential in applications such as offshore oil spill control, enhancing oil recovery and soil washing treatment of petroleum hydrocarbon-contaminated sites.

Heterologous expression, purification, and phylogenetic analysis of oil-degrading biosurfactant biosynthesis genes from the marine sponge-associated Bacillus licheniformis NIOT-06

Surfactin is a lipopeptide, composed of one β-hydroxy fatty acid, a long fatty acid moiety, and seven amino acids. In this study, the biosurfactant biosynthesis genes; 4'-pantetheinyl transferase (sfp), phosphopantetheinyl transferase (sfpO), and surfactin synthetase (srfA) have been characterized from the marine sponge-associated Bacillus licheniformis NIOT-06 from the Andaman and Nicobar Islands. The purified recombinant biosurfactant revealed excellent emulsification activity with crude oil and kerosene. Reverse-phase high-performance liquid chromatography resolved the purified recombinant biosurfactant into several fractions and one of which had significant surface tension reducing property. Fourier transform infrared spectroscopy spectrum also revealed the presence of C-N-N, alkenes, and N-H as the functional groups, and a similar overlapping pattern was observed with that of standard lipopeptide surfactin. The diversity and phylogeny of sfp, sfpO, and srfA gene sequences were compared with other eubacteria. The sfp, sfpO, and srfA gene sequences obtained from Bacillus licheniformis NIOT-06 were diverse and appeared to be partially conserved when compared with the GenBank reported sequences of several eubacteria.

Rhamnolipid biosurfactants: evolutionary implications, applications and future prospects from untapped marine resource

Rhamnolipid-biosurfactants are known to be produced by the genus Pseudomonas, however recent literature reported that rhamnolipids (RLs) are distributed among diverse microbial genera. To integrate the evolutionary implications of rhamnosyl transferase among various groups of microorganisms, a comprehensive comparative motif analysis was performed amongst bacterial producers. Findings on new RL-producing microorganism is helpful from a biotechnological perspective and to replace infective P. aeruginosa strains which ultimately ensure industrially safe production of RLs. Halotolerant biosurfactants are required for efficient bioremediation of marine oil spills. An insight on the exploitation of marine microbes as the potential source of RL biosurfactants is highlighted in the present review. An economic production process, solid-state fermentation using agro-industrial and industrial waste would increase the scope of biosurfactants commercialization. Potential and prospective applications of RL-biosurfactants including hydrocarbon bioremediation, heavy metal removal, antibiofilm activity/biofilm disruption and greener synthesis of nanoparticles are highlighted in this review.

Novel bioemulsifier produced by a Paenibacillus strain isolated from crude oil

BACKGROUND

Surface active compounds produced by microorganisms are attracting a pronounced interest due to their potential advantages over their synthetic counterparts, and to the fact that they could replace some of the synthetics in many environmental and industrial applications.

RESULTS

Bioemulsifier production by a Paenibacillus sp. strain isolated from crude oil was studied. The bioemulsifier was produced using sucrose with and without adding hydrocarbons (paraffin or crude oil) under aerobic and anaerobic conditions at 40°C. It formed stable emulsions with several hydrocarbons and its emulsifying ability was not affected by exposure to high salinities (up to 300 g/l), high temperatures (100°C-121°C) or a wide range of pH values (2-13). In addition, it presented low toxicity and high biodegradability when compared with chemical surfactants. A preliminary chemical characterization by Fourier Transform Infrared Spectroscopy (FT-IR), proton and carbon nuclear magnetic resonance (1H NMR and 13C CP-MAS NMR) and size exclusion chromatography indicated that the bioemulsifier is a low molecular weight oligosaccharide-lipid complex.

CONCLUSION

The production of a low molecular weight bioemulsifier by a novel Paenibacillus strain isolated from crude oil was reported. To the best of our knowledge, bioemulsifier production by Paenibacillus strains has not been previously reported. The features of this novel bioemulsifier make it an interesting biotechnological product for many environmental and industrial applications. Graphical Abstract Novel bioemulsifier from Paenibacillus sp.

Screening of biosurfactant producers from petroleum hydrocarbon contaminated sources in cold marine environments

An overview of literature about isolating biosurfactant producers from marine sources indicated no such producers have been reported form North Atlantic Canada. Water and sediment samples were taken from petroleum hydrocarbon contaminated coastal and offshore areas in this region. Either n-hexadecane or diesel was used as the sole carbon source for the screening. A modified colony-based oil drop collapsing test was used to cover sessile biosurfactant producers. Fifty-five biosurfactant producers belong to genera of Alcanivorax, Exiguobacterium, Halomonas, Rhodococcus, Bacillus, Acinetobacter, Pseudomonas, and Streptomyces were isolated. The first three genera were established after 1980s with interesting characteristics and limited relevant publications. Some of the 55 isolated strains were found with properties such as greatly reducing surface tension, stabilizing emulsion and producing flocculant. Isolates P6-4P and P1-5P were selected to demonstrate the performance of biosurfactant production, and were found to reduce the surface tension of water to as low as 28 dynes/cm.

Prevalence and genetic profiles of Escherichia coli from mangroves and mangrove associated foods off Goa, India

A total of 120 samples comprising of water (45), sediment (45) and mangrove originated food (30) collected from mangrove ecosystems of Goa were screened for Escherichia coli employing ISO-16654 method. Seventy-one (59.16%) samples were positive for E. coli. The E. coli isolates were further characterized by serotyping, virulence gene profiling and pulsed field gel electrophoresis (PFGE). Water and sediment samples were analyzed for physico-chemical parameters. The serotypes reported were O1, O10, O13, O17, O36, O41, O50, O68, O105, O116, O141, O148, O159, O162 and rough types while, 23 strains could not be typed. The stx1 and stx2 genes were detected in 33(46.47%) and 16(22.53%) isolates, respectively. The XbaI restriction digestion patterns of the stx positive strains were diverse. Interestingly, few strains isolated from diarrheal patients and from water, sediment and food from mangrove sources were genetically similar. The study showed that the mangrove ecosystem could be a potential reservoir for pathogenic E. coli.

Biosurfactant produced by novel Pseudomonas sp. WJ6 with biodegradation of n-alkanes and polycyclic aromatic hydrocarbons

Alkanes and polycyclic aromatic hydrocarbons (PAHs) have threatened the environment due to toxicity and poor bioavailability. Interest in degradation of these hazardous materials by biosurfactant-producing bacteria has been steadily increasing in recent years. In this work, a novel biosurfactant-producing Pseudomonas sp. WJ6 was isolated to degrade a wide range of n-alkanes and polycyclic aromatic hydrocarbons. Production of lipopeptide biosurfactant was observed in all biodegradable studies. These lipopeptides were purified and identified by C18 RP-HPLC system and electrospray ionization-mass spectrometry. Results of structural analysis showed that these lipopeptides generated from different hydrocarbons were classified to be surfactin, fengycin and lichenysin. Heavy-oil sludge washing experiments demonstrated that lipopeptides produced by Pseudomonas sp. WJ6 have 92.46% of heavy-oil washing efficiency. The obtained results indicate that this novel bacterial strain and its lipopeptides have great potentials in the environmental remediation and petroleum recovery.

Functional and molecular characterization of a lipopeptide surfactant from the marine sponge-associated eubacteria Bacillus licheniformis NIOT-AMKV06 of Andaman and Nicobar Islands, India

The production of a lipopeptide surfactant from the sponge-associated eubacteria Bacillus licheniformis NIOT-AMKV06 from the Andaman and Nicobar Islands was investigated. The highest production was attained with glucose and yeast extracts as the carbon and nitrogen sources (1.789 mg mL(-1)), respectively. The surfactant was highly stable over a pH range of 5.0-10 and a temperature range of 20-70°C with high NaCl concentrations. Excellent emulsification activity was exhibited by the purified surfactant with crude oil, kerosene, and diesel. A two-fold increase in surfactant production (3.0 mg mL(-1)) was observed using the newly formulated medium in this study. The surfactant biosynthesis gene cluster (sfp, sfpO, and srfA) from B. licheniformis NIOT-AMKV06 was heterologously expressed in Escherichia coli, and the production was increased three-fold (11.78 g L(-1)) over the original strain. The results confirm the potential of the surfactant for use in bioremediation of hydrocarbons in a marine environment and for enhanced oil recovery. To our knowledge, this is the first report on the ability of a hydrocarbon degrading B. licheniformis from marine sponges for the biosynthesis of a potent lipopeptide surfactant possessing characteristics of maximum stability, outstanding surfactant activity, and exceptional emulsifying capability.

Pyrimidine nucleotide synthesis in Pseudomonas nitroreducens and the regulatory role of pyrimidines

Control of pyrimidine biosynthesis in the commercially important, hydrocarbon-utilizing bacterium Pseudomonas nitroreducens ATCC 33634 was investigated. When glucose-grown wild-type cells were supplemented with uracil or orotic acid, the pyrimidine biosynthetic activities were depressed. Pyrimidine limitation of glucose-grown cells of an orotate phosphoribosyltransferase mutant caused aspartate transcarbamoylase and dihydroorotase activities to increase by about 4-fold while the other enzyme activities about doubled. In succinate-grown phosphoribosyltransferase mutant cells subjected to pyrimidine limitation, transcarbamoylase and dehydrogenase activities rose by about 5-fold while dihydroorotase activity more than tripled. In an OMP decarboxylase mutant, pyrimidine limitation of glucose-grown cells increased transcarbamoylase, dihydroorotase, dehydrogenase and phosphoribosyltransferase activities by 4-, 10-, 6- and 3.8-fold, respectively. Pyrimidine limitation of the succinate-grown decarboxylase mutant cells increased aspartate transcarbamoylase or dihydroorotase by more than 4-fold and the other activities by about 2-fold. Pyrimidine biosynthetic enzyme synthesis appeared to be regulated by pyrimidines with the regulation being influenced by the carbon source present. Aspartate transcarbamoylase activity in Ps. nitroreducens was regulated at the level of enzyme activity since the enzyme was strongly inhibited by UDP, pyrophosphate, ATP and ADP. Overall, the regulation of pyrimidine biosynthesis in Ps. nitroreducens can be used to differentiate it from other taxonomically related species of Pseudomonas.

Production of a bioemulsifier with potential application in the food industry

Biosurfactants are of considerable interest due to their biodegradability, low degree of toxicity, and diverse applications. However, the high production costs involved in the acquisition of biosurfactants underscore the need for optimization of the production process to enable viable application on an industrial scale. The aims of the present study were to select a species of Candida that produces a biosurfactant with the greatest emulsifying potential and to investigate the influence of components of the production medium and cultivation conditions. Candida utilis achieved the lowest surface tension (35.53 mN/m), best emulsification index (73%), and highest yield (12.52 g/l) in a medium containing waste canola frying oil as the carbon source and ammonium nitrate as the nitrogen source. The best combination of medium components and cultivation conditions was 6% (w/v) glucose, 6% (w/v) waste canola frying oil, 0.2% (w/v) ammonium nitrate, 0.3% (w/v) yeast extract, 150 rpm, 1% inoculum (w/v), and 88 h of fermentation. The greatest biosurfactant production and the lowest surface tension were achieved in the first 24 h of production, and the maximum biomass production was recorded at 72 h. The biosurfactant produced from C. utilis under the conditions investigated in the present study has a potential to be a bioemulsifier for application in the food industry.

Immunostimulation by synthetic lipopeptide-based vaccine candidates: structure-activity relationships

Peptide-based vaccines offer several advantages over conventional whole organism or protein approaches by offering improved purity and specificity in inducing immune response. However, peptides alone are generally non-immunogenic. Concerns remain about the toxicity of adjuvants which are critical for immunogenicity of synthetic peptides. The use of lipopeptides in peptide vaccines is currently under intensive investigation because potent immune responses can be generated without the use of adjuvant (thus are self-adjuvanting). Several lipopeptides derived from microbial origin, and their synthetic versions or simpler fatty acid moieties impart this self-adjuvanting activity by signaling via Toll-like receptor 2 (TLR2). Engagement of this innate immune receptor on antigen-presenting cell leads to the initiation and development of potent immune responses. Therefore optimization of lipopeptides to enhance TLR2-mediated activation is a promising strategy for vaccine development. Considerable structure-activity relationships that determine TLR2 binding and consequent stimulation of innate immune responses have been investigated for a range of lipopeptides. In this mini review we address the development of lipopeptide vaccines, mechanism of TLR2 recognition, and immune activation. An overview is provided of the best studied lipopeptide vaccine systems.

Construction and evaluation of an exopolysaccharide-producing engineered bacterial strain by protoplast fusion for microbial enhanced oil recovery

Enterobacter cloacae strain JD, which produces water-insoluble biopolymers at optimal temperature of 30°C, and a thermophilic Geobacillus strain were used to construct an engineered strain for exopolysaccharide production at high temperatures by protoplast fusion. The obtained fusant strain ZR3 produced exopolysaccharides at up to 45°C with optimal growth temperature at 35°C. The fusant produced exopolysaccharides of approximately 7.5 g/L or more at pH between 7.0 and 9.0. The feasibility of the enhancement of crude oil recovery with the fusant was tested in a sand-packed column at 40°C. The results demonstrated that bioaugmentation of the fusant was promising approach for MEOR. Mass growth of the fusant was confirmed in fermentor tests.